The response of the cometary ionosphere to space weather forcing

The Rosetta spacecraft, traversing the inner magnetosphere of comet 67P/Churyumov-Gerasimenko, observed medium-energy ions of cometary origin. These ions, moving in the direction of the cometary nucleus, are likely accelerated in the outer regions of the comet's magnetosphere. Emerging from the low-energy ion background, their signal can reach energies between 50 and 1000 eV over a few hours or days in the ion spectrum measured by the RPC IES sensor of Rosetta. Over a similar time scale, they gradually lose their energy before disappearing again from the measurements. During these medium-energy ion events, the low-energy ion background is depleted. To explain the observed temporal characteristics of the ion spectrum, we investigated the effects of the dynamic pressure of the solar wind surrounding the comet on the medium-energy ions. We demonstrated that there is a very good correlation between the solar wind pressure and the quantity of medium-energy ions detected by Rosetta: when the solar wind pressure increases, the measured amount of medium-energy ions also increases. Additionally, we observe a significant correlation between ion energy and dynamic pressure as well, although the ion energy is also influenced by other parameters, such as cometary activity and the distance from the nucleus.